Modulating compressor capacity control



Dec. 10, 1946. K. M. GERTEIS MODULATING COMPRESSOR CAPACITY CONTROL Filed Aug. 50, 1944 3 sheets sheec l INVENTOR. m4!

ATTORNEY.

Dec. 10, 1946. M, GERTEIS 2,412,503

MODULATING COMPRESSOR CAPACITY CONTROL Filed Aug. 50, 1.944 3 Sheets-Sheet 2 FIG. 2:

. INVENTOR. KM Mia/1m BY m: 2/

ATTORNEY.

'K. M. GERTEls 2,412,503

MODULATING COMPRESSOR CAPACITY CONTROL Filed Aug. 30, 1944 s Sheets- Sheet 3 INVENTOR.

ATTORNEY.

Patented Dec. 10, 1946 wnir sr'i MODULATING COMPRESSOR CAPACITY CONTROL Karl M. Gerteis, Syracuse, N. Y., assignor to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware 7 Claims.

. load requirements.

The .general object of theinvention is to provide for variably controlling theopening of one or more suction valves undercontrol of a regulating device reflecting changes in load conditions.

In employing compressors, more particularly,

refrigerant compressorsit is highly desirable to regulate capacity in order-to obtain required refrigeration effect withminimum loss of emciency.

Various attempts have been made to achieve modulating control of capacity, as by retaining open suction valves, and by other means which maintain valves in fully opened or closed positions.

Applicant provides a moreefiective solution by modulating the capacity of acompressor by regulating the graduated closing of one or more valves to reflect variations in load conditions. As a result, the disadvantages of-step control are eliminated and infinite variation in capacity throughout the effective range of the compressor may be achieved. Thus as the compressor operates under decreasing or increasing partial load conditions, the valve action varies directly to compensate for such changes in condition.

A feature or the invention resides in the use .of oil pressure variedresponsive to changes in load conditions to govern the adjustable-positioning of a suction valve.

Another feature of the invention resides inthe provision of a pair of springs, one at -each'side of a-suction valve, the extent of compression of one of them being dependent upon variations in .oil pressure reflecting-changes in load conditions.

Another feature of the invention covers the use of an oil actuated ipiston operating :a'lever device for varying the-compression of a spring bearing against one side of a suction valve to determine its time of closing as the load varies.

Another feature covers utilizing the pressure applied by'anoil actuated piston .in combination with the pressure exerted 'by a piston of the refrigerant compressor for governing the time of closing of a suction valve.

Another feature covers theregulation of oil pressure for actuating the --positioning of the suction valve responsive to temperature or pres sure conditions of anarea servedby the system of whichthe compressor is a part.

Another feature of the invention .assures the positioning of applicants control so that the compressor with respect to those cylinders to which the control is applied, starts completely unloaded.

These and other features will be more apparent from the following description of a typical form of the invention, a-ppliedto .a refrigerantcompressor, to be read in connection with the accompanying drawingsin which 4 Fig. 1.isa diagrammatic view.of a.refrigerating machine having a plurality of cylinders-applicants modulating .control being shown applied to oneof the cylinders, althougniin lpractice,.it may be applied to severalofithem.

Fig. 2 is a diagrammatic view, showing the regulating means for variously controlling the timezand duration of .openingof a suction valve on one .cylinderofa compressor.

Fig. 3 shows'a detail view of a valve, actuated by suction pressure, employed'for regulating the unloading action; and

Fig.4 shows a control arrangement for regulating oil pressure for modulating -a compressor capacity control responsive tovariations inter-n- .perature conditions of an area served-by .an.=air

.rods 22 and other structural elements normally employed for compressing gases, all of which form no essential part-ofthe-invention, but which it will be understood arepresent to forman operable compressor.

In various applications to 'whichiacompressor may be applied, more especially a refrigerant compressor, the need for varying the output responsive to difierent or changing loa'd {requirements is often great. Applicant provides a modulating control adapted to be applied to one or more cylinders of a compressor for governing the action of the suction valve serving the cylinder to which the control is applied. Unlike previous .expedients for controlling compressor capacity, the action of applicants valve is -so regulated that the time and extent of opening of :said

valve is correlated with variations inload re- .quirements with the result. that compressor 'out-.

put will automatically be increased or decreased exactly to compensate for changes in load.

First considering the general diagrammatic arrangement of Fig. 1, pump l4 supplies oil from sump H to feed line l5. The oil passes through orifice I6 and then applies pressure within supply line depending upon the amount of oil flowing through regulating line |8 which is routed to control valve l9 from which the oil fed thereto is returned to the sump through return line 20. Suction pressure connecting line 2| subjects control valve 9 to the suction pressure in manifold 52.

Now considering the detailed view shown in Fig. 2 of applicants modulating control as applied to any desired cylinder, a power element 23 has a piston 24 therein with a piston rod 25 connected to a forked operating lever 26 at pivot 21. The lever is connected at pivot 23 to power element cover 29. A spring 30 is positioned about piston rod 25 between the inverted piston head 24 and cover 29. Actuating shoes 3| at the ends of the forked operating lever 26 bear against spring supporting ring 32 to cause the ring to move up and down upon the outer wall of the cylinder guided by bodyportion 33 of ring 32 which is positioned concentrically about the cylinder.

A plurality of capacity control springs 34 are mounted upon supporting ring 32 within suction ports 35 of cylinder sleeve 36. Suction valve 31 is positioned between capacity control springs 34 and suction valve springs 38, the valve springs beingrecessed in the usual man: ner within valve plate 39.

The control valve l9 which regulates the pressur applied to power element 23 is shown in detail in Fig. 3. The oil from pump l4 feeds into valve l9 through regulating line H? entering port 40. The oil passes through drilled passageway 4| past valve seat 42 into passageway 43 depending upon the position of valve needle 44, the position of which is determined by the action of bellows element 45.

The bellows element includes cup 46 having therewithin a range adjustment spring 41 whose compression is adjusted by the regulating screw 48. The cup actuates a series of push pins 49 which, in turn, bear against collar 59 for positioning the valve needle. The collar has exerted thereagainst the pressure of spring 5| in opposition to the force supplied thereto by the pins.

Suction pressure reflecting the condition in suction manifold 52 is applied through line 2| and passage 53 to the inside of bellows 45. The 'result is that as the suction pressure drops, the

cup 46 will move downwardly to cause pins 49 to open the valve, causing an increase in oil to flow through regulating line |8 with the result that oil pressure through line H exerted upon power element 23 will drop. On the other hand on an increase in load, when the suction pressure rises, the pressure in the bellows will correspondingly rise to overcome the pressure of spring 41, with the result that spring 5| will serve to tend to push the valve needle to closed position. The pins 49, in this event, will not be able to overcome the pressure of spring 5| since the cup will be suficiently lifted due to the increased pressure within the bellows to keep the pins from pushing downwardly collar 59 in which the valve needle is held.

The push pins 49 fit within holes in the valve casting so that they ride up and down resting against the bottom of the cup 46 and the top of collar 50. As the cup tends to rise upon expansion of the bellows, the action of spring 5| will serve to close the valve and make the pins ride up, whereas when the bellows contracts, the pressure of spring 41 which is then greater than the pressure of spring 5|, will cause the pins to push down the collar and hence open the valve.

In practice, with the system shown in Figs. 1 and 2, including a control valve l9 as shown in Fig. 3, it will be noted that when the compressor is started up, substantially no oil pressure will exist at the moment of starting. Consequently, there will be no oil pressure in line H and the piston 24 of power element 23 will be down. Thus, actuating shoes 3| will be in uppermost position holding spring supporting ring 32 in top position with suction valve 3'! completely open. The compressor will, therefore, start in an unloaded condition, as is most desirable.

Under practical operating conditions, when the suction pressure is above the point for which regulating screw 48 on valve I9 is set, then the modulating mechanism will be inoperative. However, upon a drop in suction pressure below said set point, the valve needle will open to reduce the oil pressure in an amount depending upon the reduction in load, as reflected by the drop in suction pressure. The efiect is to apply a varying pressure upon the power element 23 corresponding to the variation in partial load. Consequently, the suction valve 31 will be opened at a point in the stroke and then closed responsive to building up of pressure upon the compression stroke to provide less than full compressor capacity corresponding to the drop in load.

In Fig. 4, a modified form of control is illustrated in combination with an air conditioning system served by a compressor equipped with applicants invention. In this case, a multi-cylinder compressor has one or more of the cylinders equipped with the capacity control already shown in Fig. 2. The gas discharged from the compressor goes to a condenser 54, receiver 55, then through expansion valve 56 to an evaporator 51 employed for cooling the air of enclosure 53; the gas returning to the compressor through line 59 to close the usual cycle.

Instead of operating applicants modulating control responsive to variations in suction pressure, a regulating device 60 is provided operative responsive to a thermostatic bulb 6| within the conditioned enclosure 58.

The position of diaphragm 62 of regulating de Vice 6!] depends upon the pressure within lower diaphragm chamber 63 and the spring pressure of spring 64.

Upon a decrease in room temperature, indicating a drop in load, diaphragm 62 will tend to move down to open the valve in an amount corresponding to the reduction in load. 0n the other hand, upon an increase in temperature within the conditioned enclosure the pressure within chamber 63 will increase to the point where it overcomes the pressure of spring 64 and correspondingly tends to close the valve 65. The oil pressure in line II will then rise to cause the piston in the power element to go up whereupon the supporting ring 32 will drop and suction valve 31 close to resume full load operation. Of course, where partial load conditions still obtain, the action will be the same as with the control of Fig. 3 in that the time and extent of opening of the suction valve will be governed by the partial load condition which regulates the spring action on the valve as opposed to the compression on the'upward stroke of the cylinder.

Thus, applicant provides a sensitive modulating control with unlimited range for every load condition which arises over practical operating conditions. The compressor starts in unloaded condition. Immediately thereafter, however, it may operate at full load conditions; and thereafter whenever partial loads are encountered the capacity will be increased and decreased to compensate for such variations in partial load to give exactly the capacity needed to maintain any given condition.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

I claim:

1. A system of modulating capacity control for reciprocating compressors comprising means for pumpingoil, an oil actuated power element, a line including an orifice therein for delivering oil under pressure to said power element, a modulating means operative responsive to variations in load conditions affecting a compressor for modulating the oil pressure in said line, a suction valve, and means operated by the power element for varying pressure applied against the valve to determine its time of closing.

2. A modulating capacity control for a reciprocating compressor, including a suction valve, a suction valve spring bearing on one side of the valve, a capacity control spring bearing against the valve on the other side thereof and means responsive to varying oil pressure for compressing the capacity control spring depending upon variations in load conditions affecting the compressor.

3. A modulating capacity control for reciprocating compressors including a power element, a piston within the power element, means for applying oil pressure to said power element opposed by spring pressure thereon, an operating lever under control of the power element, a suction valve, means for applying pressure against the suction valve, said means being actuated by said lever and means for varying the oil pressure exerted on said power element for correspondingly varying the pressure applied against said suction valve.

4. In combination with a compressor, including a modulating capacity control therefor, a suction valve, a pair of springs positioned on opposite sides of the valves, means for compressing one of the springs in accordance with variations in load affecting the compressor.

5. In combination with a reciprocating compressor, a modulating capacity control for regulating the time of closing of a valve, said combination including a valve, means for applying a force in one direction against one side of said valve, means for applying a force in the opposite direction against the opposite side of said valve, means for varying the force applied against the opposite side of the valve responsive to variations in load affecting the compressor.

6. In a combination of the character described, a compressor having a plurality of cylinders, a modulating capacity control applied to certain of said cylinders, said capacity control including an operating lever on each of a plurality of said cylinders, an oil pressure actuated power element controlling the movement of said lever, a spring supporting ring adapted to be variously positioned by said lever, a capacity control spring supported by said ring and bearing against one side of said valve, means for supplying spring pressure against the other side of said valve, an oil pump for lubricating the compressor, and means for supplying oil from said pump to the power element at a pressure depending upon the load aifecting the compressor to govern the pressure exerted by said first mentioned spring bearing against the valve.

'7. A system for varying the output of a compressor including a valve in the compressor, means for. exerting spring pressure on opposite sides of the valve, a power element operated by oil pressure for modulating the spring pressure applied to one side of the valve, an area to be conditioned served by the compressor, and means operative responsive to variations in atmospheric conditions within said area for varying the oil pressure applied to said power element in such a manner that said spring pressure controlled thereby is varied to adjust the time of closing of the valve to regulate capacity output of the compressor" in accordance with changing load conditions in said area.

KARL M. GERTEIS. 

